Frequency multiplier and amplifier



Sept. 20, 1932. c. w. HANsELL FREQUENCY MULTIPLIER AND AMPLIFIER je?! m D( M v M v 2 Sheets-Sheet 1 Fig 2 INVENTOR C.W.'HAN$ELL BWM MM A TORNEY Sept 20 1932- c. w. HANsELl. 1,878,308

` FREQUENCY MULTIPLIER AND AMPLIFIER Filed March 23. 1927 2 Sheets-Sheet 2 Rfanvmnrlvr Ffm .9 lack #on numwomc Lg GJCILLATIUN SOURCE TTORNEY Patented Sept. 20, 1932 UNITED STATES PATENT` OFFICE CLARENCE W. HANSELL, OF ROCKY POINT, NEW YORK, ASSIGNOR TO RADIO CORPORA- TION 0F AMERICA, A CORPORATION 0F DELAWARE FREQUENCY MULTIPLIER AND AMPLIFIER Application mea mma 23, 1,927. serial No. 177,505.

This invention relates to frequency multipliers, and more particularly to a method and meansI for obtaining frequency multi- `plication and amplification in the successive power stages of a short wave transmitter.

Crystal control is desirable in order to maintain constant frequency, but it is found that crystals ground to have a frequency greater than that corresponding to about a 100 meter wave are too delicate for practical handling and utilization. Modern practice dictates the use of waves as short as 15 meters, and even less, and accordingly it is an object of my invention to make possible the use of a low frequency crystal for the control of a high frequency transmitter. This I do by employing frequency multiplication in the successive power stages of the amplifier of the transmitter.

The use of frequency multiplication with crystal control is not new, but heretofore it has been customary to use such frequency multiplication only for external controlling energy obtained from a master oscillator. The high frequency low power output from the master oscillator was used to control the frequency of power amplifier systems, 'all the stages of which were tuned to the high frequency. This method was used because it was the most obvious one and because vacuum tubes have not been considered eiiicient from an energy standpoint when used as frequency multipliers. The frequency multiplication has therefore been restricted to the small frequency control energyalone.

However when short waves with correspondingly high frequencies are used great difliculty is encountered due to'feed back of energy from the output circuit to the input circuit of each stage of the amplier, which tends to make the stage oscillate independently of the frequency control energy, and also due to energy feed back from the higher power to the lower power stages of the amplifier, which tends to cause the whole chain or system of amplifiers to oscillate independently of the frequency control energy.

The principal object of my invention is to eliminate this difficulty due to feed back of energy and to prevent the tendency for oscillation independent of the control energy. Thls I do by multiplying the frequency of the control energy ineaeh stage of the ampllfier. When this is done the effect of feed back from the output to the input circuit of each stage of the amplifier is very greatly reduced because lthe circuits are tuned for and operate at greatly different frequencies. The input circuit does not respond to currents from the output circuit because it is not tuned for the frequency of these currents and therefore it does not cause radio frequency potential to be brought backto the control electrode in a manner to cause oscillation such as would obtain in the ordinary amplifier where the input circuit is tuned to the frequency of the current in the output circuit. Also the effect of feed back from the higher power to the lower power stages is very greatly reduced because of the very great difference in the operating frequency for which each stage is tuned. A still further gain is made in freedom from feed back diiiculties because all stages but the last operate at lower frequencies than the final output from the system and this lower operating frequency in itself lessens the amount and effect of the feed back of energy.

A further object of my invention is to improve the energy etliciency of a vacuum tube when used as a frequency multiplier and amplilier at the same time. This I do by adjusting the power stage in which the tube is used so that anode currents How for only a brief fraction of the time duration of a half cycle. In the next place, I have found that at high frequencies, because the magnitude of the tube capacitance becomes great relativeto the input circuit capacitance, there is an appreciable degenerative effect. Although this effect is very much less than in a. stage used as an ampliiier without fre uency multiplication, still it is very-bene cial at'the higherl frequencies to compensate for this degeneration. This compensation may even be carried beyond the point where the degeneration becomes zero and some regeneration may be 4used without causing oscillation, as would be the case in the ordinary amplifier, and this improves the energy eflici'ency of the vacuum tube. This compensation of the degeneration, or else positive regeneration, by the addition of regeneration of the same amount or else more than the degeneration is accomplished by bringing energy back from the output circuit at the harmonic output frequency and with it applying a potential to the grid of the tube which is opposite in phase to the harmonic high frequency potential on the anode.

By making the amplifier stages efficient although used as frequency multipliers my invention obviates the necessity for using separate frequency multipliers .and their associated equipment and thereby saves both in original outlay and in power consumption.

It is sometimes desirable to arrange a frequency multiplier and amplifier stage to obtain an even harmonic, with consonant suppression of the odd harmonics, or an odd harmonic with suppression of the even harmonics. In still other cases it may prove desirable to have a single arrangement which is capable of delivering either an odd or an even harmonic. Accordingly, it is a further object of my invention to provide circuits for even harmonic, odd harmonic, and all harmonic amplifiers.

The more complete specification which fo1- lows is accompaniedfby drawings in which:

Figure 1 shows potential and current curves for eficient frequency doubling;

Figure 2 is a wiring diagram for an amplier stage;

Figure 3 shows potential curves for the circuit in Figure 2;

Figure l is a wiring diagram for an all harmonic amplifier;

Figure 5 is the circuit of Figure 1 rearranged in the form of a bridge Figure 6 is a wiring diagram for an even harmonic amplifier;

Figure 7 is the'circuit of Figure 6 rearranged in the form of a bridge Figure 8 is a wiring diagram for an odd harmonic amplifier; and

Figure 9 is the circuit of Figure 8 rearranged in the form of a bridge.

In Figures 5, 7 and 9 certain immaterial elements have been omitted.

It is possible to get very nearly full rated power from a tube even though used for an output frequency which is a multiple of the input frequency. Referring` to Figure 1 it will be seen that the curve of grid voltage eg, which is substantially the same as that for any vacuum tube amplifier when adjusted to operate at'high efficiency, swings above the line of holding or grid biasing potential only at the peak of the positive half cycle of input potential. In consequence 'the plate current D flows during only a brief fraction of the duration of a positive half cycle of input potential. With this condition there may be obtained in the plate circuit a plate voltage n flows only during the short interval of time during which cp is passing through its most negative values, and at that time cp is the same for both the fundamental frequency and the harmonic frequency, it follows that the product pep is almost as great for operation on the harmonic as for operation on the fundamental. This efficient production of harmonics without reduction in energy output from the tube can, of course, be anticipated only when limiting the operation to the'lower harmonics.

Referring to Figure 2, input energy is fed by means of the coil L1 to a coil Lg, which, together with the condenser Cg, forms an input circuit tuned to the input frequency. The output circuit CpLp is' tuned -to the harmonic frequency, and is connected to the cathode by condenser Cl and a direct current source. There is a natural tube capacitance, represented by CT. The grid 'is maintained at the biasing or holding potential by, for example, any suitable source of negative biasing potential of suitable value. As shown in Figure 1, the biasing or polarizing potential of the grid of the tube 2 of Figure 2 is maintained at a proper negative bias such that plate current fiows during only a brief fraction of the duration of a half cycle of positive input alternating potential. Accordingly, with the single tube arrangement of Figure 2, when the output circuit is tuned to a harmonic of the input, it oscillates freely for a period of time greater than the time of a harmonic cycle before another impulse of excitation energy is received fromthe plate.

For the 'higher harmonic frequencies the input circuit becomes an effective capacitance, because the inductive reactance is increased and the capacitive reactance is decreased. We may therefore consider that there is a circuit from the anode to the filament consisting of the two condensers CT and the effective capacity of the input circuit in series. At very high frequencies the capacitance Gg becomes small, and the capacitance CT becomes quite large relative to CE, consequently we can no longer assume that most of the potential drop from anode to filament takes place across the capacitance CT. As the reactance of CT decreases the potential drop across it decreases andconsequently a larger portion of the total potential fluctuation takes place across Og, and it is this potential fluctuation measured across the grid condenser which is effective at the grid. In general the grid and anode potentials fiuctuate 180 degrees out of phase,

Awith the anode potential,

but this feed back energy is practically in phase, and therefore is degeneration.

'lhese relations are shown by the curves 1n Figure Curve A represents the grid potential of fundamental frequency; curve 13 shows the resulting anode potential if the anode circuit is tuned for the fuiulaniental; curve C represents the anode potential if the anode circuit is tuned to the. double frequenc v', and it is to be noted that this curve, like curve B, is in phase opposition to the grid potential during the positive or effective half-cycles of the latter; and curve I) shows the grid potential caused by feed back through the condenser C., and this is in phase as shown\by curve C, thus causing degeneration.

Attention. is now directed to Figure 4, which is similar to Figure 2 except that the steady anode potential is applied at point y, the midpoint of the induct-ance Lp. and there has been added a condenser CN. lf the condenser CN is adjusted to equal CT in capacitance the output circuits are thereby made symmetrical with respect to the grid, and the circuit is neutralized.

As in the arrangement shown in Figure 2,

and as described in Figure 1, the grid of the frequency multiplier tube of Figure 4 is maintained at a 'negative potential such that plate current floivs'only during a brief fraction of the positive half cycle of input potenf v tial.

Figure 4 has been redrawn in Figure 5 in the form of a bridge. It is clear that since points a and 1/ are each at mid-potential with respect to the alternating anode potential across the bridge at points a and there can be no potential difference between points and y, for the harmonic frequency, and consequently none across the condenser C, as a result of which there will no longer be degeneration.

In order to obtain regeneration in an exceedingly simple manner, according to my invention N is made to have greater capacitance than CT, that is, the circuit is overneutralized. From the diagram in Figure 5 it can' be seen, if condenser CN is made greater than CT in capacitance, and therefore less in reaetance, that point w, instead of heilig at mid-potential or ground potential With reference to the anode harmonic frequency', will have a potential value dependent upon the difference in the capacitance, that is, upon how far away from the mid-point of the cathode-anode potential gradient the grid is shifted, electrically, and that this potential will be 180 degrees out of phase with respect to the anode potential. The circuit then is regenerative.

The arrangement so far described is an all harmonic amplifier, equally Well adapted for the production and amplification of even or odd harmonics.

If it is desired to arrange the stages so that. each will utilize two tubes arranged with their' control electrodes in phase opposition it becomes necessary to use a special circuit according as even or odd harmonics are to be developed. It is quite easily arranged, if the fundamental frequency is multiplied to an even harmonie, that the odd harmonics be completely suppressed, and vice versa. The use of two tubes is often desirable not only to get an increased energy output but also because. if they are oppositely excited they deliverenergy to the output circuit at more frequent intervals than when a single tube is used and so a pure undainped continuous wave current is more closely approached in the output circuit.

`he relation between the anode current and potential in a vacuum tube may be expressed by the equation i2/1E" in which A and de- .pend upon the characteristics of the tube. Letting i,.l=the anode current in the first tube, W2-:the anode current in the secondtube, ]L"=tl1e steady anode potential, u=the amplification factor of the tubes, E=. the steady grid potential, c=the maximum alternating grid potential, and

evt-:the input frequency, we may write:

'uit is the input energy applied to the tube grids, and since these are 1n phase opposltion,

loe

there is a difference in algebraic sign, as indictated. If these expressions are expanded into series and rearranged to shov7 the harmonics it is found that the even harmonics have like algebraic signs, and the fundamental and odd harmonics have unlike algebraic signs. To indicate the idea in a very simple Way assume that the exponent has a value of 2. v

Substituting 2 for ai, expanding to remove the exponent, and then substituting for sin2wt its value in terms of double the angle,

1 eos Z'wt,

2 We obtain damental frequency. It 1s important to notice that if the outputs of the two tubes are added algebraically then the second harmonie' out uts of each will be combined in phase, while the fundamental will be combined out of phase, and eliminated. On the other hand, if the outputs of the two tubes are combined subtractively, then the even h armonie is eliminated, and the fundamental is added in phase.

In actual practice the exponent is not 2, but is variable over a wide range in the course of a single cycle, and Various other harmonics are cancelled and the odd harmonics are obtained.

In Figure 6 there is shown an even harmonic amplifier. Input energy is supplied to the coil L1, which is coupled to the coil Lg. The latter, together with the capacitance represented by the series combination Gg, and Ggg, forms an input circuit which is timed to the input frequency, and which is connected, as shown, to the grids of the tubes T1 and T2 in series, or phase opposition. The anodes of the tubes T1 and T 2 are directly connected inI parallel to one side, b, of the output circuit GpLp, which is tuned to an even harmonic of the input frequency. rI`his connection gives algebraic addition of the tube outputs, and the desirability of this was before pointed out. The other side of the output circuit, a, is connected through a neutralizing and regenerative feed back condenser GN to the mid-point of the potential gradient across the input tuning condensers. The circuit from anode to cathode -is madev from point y, which is at the mid-point of the alternating potential gradient across the output circuit, through a blocking condenser G1 and a source of direct anode potential, not shown. The natural tube capacitances are indicated by GTL and As described in connection with the curves of Figure l, the grids of the tubes of the circuit shown in Figure 6 are maintained at a negative potential such that only the peaks of positive input potential cause plate current to flow.

The circuit has been redrawn in the form of a bridge in Figure 7, and it is easily seen from this figure that GN may be given a value which will make the points w1 and x2 be at mid-potential, or ground potential, and therefore have the saine potential as mid-point y in the output circuit, in which case there will be no degenerative potential applied to the grids G1, G2. As before explained, in accordance with my invention the capacitance GN may not be adjusted for exact neutralization, but instead may be so adjusted that the points m1,

m2 are moved above the mid-point on the potentialgradient between a and thereby placing upon the grids G1 and G2 a potential .of frequency equal to the output frequency,

and in phase opposition with respect to the potential on the anodes P1 and P2, thereby increasing the amplification.

lf odd harmoni's are desired and even harmonics are to be suppressed, it is merely necessary to arrange the output circuit as well as the input circuit in series or phase opposition with respect to the tube electrodes.` Such a circuit has been shown in Figure 8, in which Lg Gg is an input circuit, tuned to the input frequency, and connected to the tubes T1, T2 in phase opposition, while Gp Lp is an output circuit, tuned to an odd harmonic of theinput frequency, and connected to the tube anodes in series or phase opposition, that is, it is so connected to the tubes that their outputs are combined subtractively, in contra-distinction to the arrangement in Figure (S in which the outputs of the two tubes are combined additively.

Natural tube capacitance is represented by GT, and GT2, and to provide regeneration the feed-back condensers Gm and GNQ are connected as shown. This arrangement is quite similar to a neutralizing arrangement already known in the art but this prior neutrali zing arrangement has not been applied to a frequency multiplier. Also it is important to note that the so-called neutralizing condensers may be made greater than the tube capacitance in order to. obtain regeneration in a most simple manner and without such a great tendency for oscillation as is met with in the ordinary amplifier used in the prior art.

In the arrangement shown in Figure 8, the grids, as described. in connection with Figure l, are maintained at a negative potential such that `plate current flows only during a brief portion of the peak of positive input potential applied to each tube.

Figure 9 shows the circuit of Figure 8 redrawn in the form of a bridge. When Gm is made equal to GTl, and GNgvis equal to GT2, the grids G1 and G2 are at mid-potential or ground potential with respect to the output frequency, although, of course, their potentials vary oppositely at the input frequency. When the condenser GN1 is made larger than natural capacitance GTI, point mi moves downwardly on the potential gra-dient between a and I), whereby potential of the output frequency but of opposite phase to that upon the anode P1 is impressed on the grid G1, resulting in regeneration. Similarly, when the condenser GNZ is made greater' than the natural capacitance GT2, point m2 moves upward with respect to mid-potential, and

therefore varies at output frequency in opposite phase with respect to the anode P2. In eect, the grids G1 and G2 vary in phase opposition with one another, at output frequency, and this is in effect a push-pull 1nput at the output frequency, serving to accentuate the harmonic.

In all of the arrangements disclosed -it may be mentioned that because the input circuit is not tuned to the output frequency the adjustments for regeneration are not at all critical, and the desired amount of regeneration may be easily approached Without danger of swinging over into self-oscillation. This is in marked contrast to the extremely critical adjustment required to prevent oscillation of the ordinary amplifier when used at very high frequencies. I have found that at frequencies corresponding to 15 meters variations in capacitance of tubes and circuits due to mechanical movement resulting from temperature variation is alone suflicient to seriously handicap continuous operation of the ordinary amplifier.

In actual practice it is found that the amplifier stages may be operated almost as efiicientlj-7 and -almost at the same power rating on a low harmonic as on the fundamental With the further advantage that the trans'- mitter is greatly simplified, not only by the entire omission of special frequency multipliers for a master oscillator, but also by reason of the fact that only the output circuit of the last stage need be accommodated to the high transmission frequency, and each of the preceding circuits operates at progressively lower and more easily handled frequencies, with which only a sma-ller percentage of energy need be Wasted in c1rcu1t losses.

The foregoing modifications have been disclosed by way of illustration andnot limltation of my invention, which I claim is:

1. In apparatus of the character de-l scribed, an electron discharge device having Within an hermetically sealed container an electron emitting cathode, an electron receiving anode, and a control electrode intermediate said cathode and anode for controlling the lovv of electrons from said electron emitting cathode to said anode, a circuit comprising an inductance coil and a. condenser connected in parallel connected across said Icontrol electrode and cathode, said circuit being tuned to a fundamental frequency, a circuit comprising an inductance coil and a condenser connected in parallel connected between said anode-and cathode, the circuit constants of said last mentioned circuit being such as to resonate at a frequency corresponding to a harmonic of the frequency of said circuit connected across said lcontrol electrode and cathode, means for subjecting said control electrode to a negative potential With respect to said cathode, and means for energizing said circuit connected across said control electrode and cathode with energy of fundamental frequency corresponding to the tuning of said circuit connected across said control electrode and cathode, the control electrode of said electron dlscharge device .being subjected by said negative biasing means to a negative potential of a value such that for only brief fractions of positive input alternating potentials applied to said control electrode, plate current flows through said device from said cathode to said anode, whereby said circuit connected between said anode and cathode is caused to have engendered therein electrical oscillations of harmonic frequency, which oscillations oscillate freely for periods of time greater than the time of a cycle at the harmonic frequency intermediate successive times when plate current -lows through said tube from said cathode to said anode.

2. In combination, an electron discharge device; a tunable input circuit tuned to a fundamental frequency directly connected to the input terminals of the electron discharge device; a tunable output circuit,

tuned to a harmonic of the fundamental frequency, directly connected to the output terminals of the electron discharge device; and means for subjecting the control electrode of the device to a negative potential such that only narrow positive peaks of a funda-- mental frequency input energy cause anode current to flow. l.

3. lIn apparatus for increasing the frequency of undulatory electrical currents, an electron discharge device having Within an evacuated container, an anode,'a cathode, and agrid, an input circuit coupled to said grid and cathode tuned to a fundamental frequency; an output circuit coupled to said anode and cathode tuned toa harmonic frequency, means for polarizing electrodes of said device so that energy of fundamental frequency appearing in said input circuit causes energy of harmonic frequency corresponding to the frequency of the tuning of the output circuit, to flow in the output circuit, and, means for rendering ineffectual the interelectrode capacitance between output and input electrodes of said electron discharge device.

4. In combination, an electron discharge device; a tunable input circuit tuned to a fundamenta-l frequency directly connected to the input terminals of the electron discharge. device; a tunable output circuit, tuned to aharmonic of the fundamental frequency, directly connected to the output terminals of the electron discharge device; means for subjecting the control electrodey ofthe device to a negative potential such that only narrow positive peaks of fundamenta-l frequency input energy cause anode current to flow; and, means for rendering ineffectual the capacitance between the input and output electrodes of said device.

5. In the operation of a frequency multiplier including an electron emission tube having natural capacitance and an input cirtion or unsymmetrically for over neutraliza-- cuit therefor the reactance of which 'cap-acitive for the harmonic frequency, the method of obtaining large output energy of harmonic y frequency which includesthe step of neutralizing or over-neutralizing the degeneratlve' quency obtained from a frequency multiplier' and amplifier stage employing a three electrode tube which includes arranging the tube output circuit symmetrically for neutralization and thereby applying potential of harmonic frequency from the output circuit of the stage to the control electrode of the tube in phase opposition relative to the potential of harmonic frequency on the anode of the tube; A

7. The method of obtaining large high frequency output from; a neutralized power stage of a transmitter which includes the steps of feeding input energy to the input circuit of the stage, tuning the input circuit to the input frequency, tuning the output circuit to` a harmonic of the input frequency, and applying from the output circuit to the input circuit an excess of neutralizing energy of the harmonic frequency.

8. The method of tuning a neutralized power stage of a transmitter to obtain frequency multiplication and amplification which includes the steps of tuning the input circuit to the input frequency, tuning the output circuit to one of the lower harmonics of the input frequency, and adjusting the neutralizing circuits to transfer more than the requisite amount of energy for true neutralization.

9. The method of tuning a capacity neutralized stage of a transmitter to obtain frequency multiplication and amplification which includes the steps of tuning the input circuit to the input frequency, vtuning the output circuit to one of the lower harmonics of the input frequency, and adjusting the neutralizing condensers to values greater than that needed for true neutralization in order to obtain Vregenerative amplification of the harmonic frequency.

10. Infrequency multiplying and amplil fying by means of a single power stage having two electron emission tubes, the method of selectively discriminating between even and odd harmonics which includes supplying input energy to the tubes in phase opposition, and directly resonantly collecting all of the output'energy from the tubes either additively or subtractively alone according as even or odd harmonics are desired.

11. In frequency multiplying by means of a single power stage having two electron emission tubes with series connected grids, the method of selectively discriminating beaugmenting the usual tween even and odd harmonics which includes directly resonantly combining the tube outputs either directly in parallel or directly in series alone according as even or odd harmonics are desired. A

12. In frequency multiplying and amplifying by means of a single power stage havingl two electron emission tubes with series connected grids, the method of selectively discriminating between even and odd harmonics and amplifying the harmonic desired which includes combining the tube outputs 1n parallel or in series according as even or odd harmonics are desired and feeding a portion of the harmonic output energy to the mput energy in proper phase for regenerative amplification of the harmonic outputJM energy.

13. In frequency multiplying and amplifying by means of a single power stage having two electron emission tubes with series connected grids, the method of selectively discriminating between even and odd harmonics and amplifying the harmonic desired which includes combining the tube outputs in parallel o'r in series according as even or odd harmonics are desired and feeding a portion of the harmonic output energy to the input energy in proper phase for opposing i energy transferred thru natural tube capacitance. l

14. In frequency multiplying and amplifyingby means of a single power stage having two electron emission tubes with series connected grids, the method of selectively discriminating between even and odd harmonics and amplifying the harmonic desired which includes combining the tube outputs' in parallel or in series according as even or odd harmonics are desired and feeding a portion of the harmonic output energy to the input energy in proper `phase for neutralizing energy transferred thru natural tube capacitance, but in excess magnitude in order to obtain regenerative amplification of the harmonic outputenergy.

15. In frequency multiplying by means of a single power stage having two electron emission tubes, the method of selecting an even harmonic and eliminating the fundamental and odd harmonics which includes supplying input energy to the tubes in phase opposition and directly resonantly collecting all of the output energyI from the tubes in parallel. Y

16. In frequency multiplying and amplifying by means of a single power stage having two electron emission tubes, the method of selecting and amplifying an even harmonic and eliminating the fundamental and odd harmonics which includes supplying input energy to the tubes in phase opposition, collecting output energy from the tubes in parallel, and feeding a portion of the harmonic output energy to the input energy in proper phase for regenerative amplification of the Vharmonic output energy.

17. In frequency multiplying and amplifyingr by means of a single power stage having two electron emission tubes, the method of yselecting and amplifying an even harmonic and eliminating the fundamental and odd harmonics which includes supplying input energy to the tubes in phase opposition, collecting output energy from the tubes in parallol, and feeding a portion of the harmonic output energy to the input in proper phase for opposing energy transferred th-ru natura] tube capacitance.

18m In frequency multiplying and amplifying by means of a single power stage having two electron emission tubes, the method of selecting and amplifying an even harmonic and eliminating the fundamental and odd 20 harmonics which includes supplying input power' stage for peaks of the input energy cause 4- i tuned to 5 said tube, and means to energy to the tubes in phase opposition, collectin g output energy from the tubes in parallel, and feeding a portion of the harmonic output energy to the input energy in proper phase for neutralizing energy transferred thru natural tube capacitance, but in excess magnitude in order to obtain regenerative amplification of the harmonic output energy.

19. A frequency multiplier and amplifier a transmitter comprising an electron emission tube, an input circuit tuned to an input frequency directly connected thereto, an output circuit tuned to a harmonic of the inputfrequency, directly connected to regeneratively couple the output circuit to the input circuit to accentuate the harmonic frequency, the control electrode of said tube being subjected to a negative potential such that only narrow positive output current flow through said tube.

.20. A frequency multiplier and amplifier stage comprising an electron emission tube having natural capacitance, an input circuit 'an input frequency, an output eircuit tuned to av harmonic of the input frequency, and neutralizing means adjusted to feed more energy than is needed for neutralizing the energy transferred thru the natural tube capacitance.

2l. A frequency multiplier and amplifier power stage comprising two electron emission tubes, an input circuit arranged to energize the tubes in phase opposition, a parallel resonant output circuit tuned to an even harmonic of the input frequency, and means to feed the output from both of the tubes directly in parallel to the resonant output circuit.

22. A frequency multiplier and amplifier power stage comprising tWo electron emission tubes having natural capacitance, an input circuit arranged to energize the tubes in phase opposition, an output circuit tuned to an even harmonic of the input frequency, means to connect said tubes to said output circuit in parallel, and means to supply from the output circuit to the input circuit energy of the harmonic frequency in such phase as to oppose the effect of energy transferred thru the natural tube capacitance. 23. A frequency multiplier and aniplifier power stage comprising two electron cinissfon tubes having natural capacitance, an input circuit arranged to energize the tubes in phase opposition, an output circuit tuned to an even harmonic of the input frequency, means to connect said tubes to said output circuit in parallel, and means to supply from the output circuit to the input circuit energy of the harmonicvfrequency in such phase as to oppose the effect of energy transferred thru the natural tube capacitance and of excess magnitude in order to obtain regenerative amplification of the harmonic frequency.

24. A frequency multiplier and amplifier power stage comprising two electron emission tubes, an input circuit comprising an inductor and a condenser tuned to an input frequency and connected to the tubes in phase opposition, an output circuit con'iprising an inductor and condenser tuned to an even harmonic of the input frequency, means to connect both of said tube anodes to one side of the output circuit, means including a neutralizing condenser connecting the other side of said output circuit to the mid-potential point of the input circuit condenser, and means including a source of energy connecting the cathode to a mid-potential point of the output circuit.

25. In the operation of a power amplifier comprising cascade connected stages having tuned input and output circuits for the delivery of very high frequency power the method of stabilizing the delivered frequency by preventing spurious oscillations and rendering the tuning adjustments of the amplifier stages less critical which includes the step of frequency multiplying in the amplifier stages whereby only the last circuit is tuned to the very high frequency, and all of the circuits in the amplifier are tuned to frequencies different from one another, and, the step of biasing each amplifier such that only narrow positive peaks of input potentials cause energy fiowin the output circuit of the amplifier.

26. In the operation of a frequency multiplier stage including an input circuit tuned to the lower frequency, an output circuit tuned to the higher frequency, and an electron emission tube having natural capacitance thru which degenerative energy of the higher frequency is passed, the method of making the multiplier stage more highly effective as an amplifier stage which includes neutralizing the multiplier stage in order to overcome degeneration. v

27. The combination with a frequency multiplier stage having natural coupling which permits the transfer of degenerative energy between the lower and higher frequency circuits, of means to transfer energy of like 'frequency and opposite phase to counteract the naturally transferred degenerative energy.

28. The combination with a frequency multiplier stage including an electron emission tube having natural capacitance and an input circuit which is capacitive in reactance for energy of the multiplied frequency, of means to neutralize the stage for the natural capacitance of the tube.

29. In the operation of a frequency multiplier including an electron elnission tube having `natural capacitance, an output circuit tuned to a harmonic frequency and an in! put circuit tuned to a fundamental frequency whereby it is an effective capacitance for the harmonic frequency, the method of increasing the output energy of harmonic frequency which includes applying regeneration tending to overcome degeneration caused by the tube capacitance being electrically in series with an effective grid-to-iilament capacitance for the harmonic frequency.

30. In combination, an electron discharge device; a tunable input circuit tuned to a fundamental frequency directly connected to the input terminals of the electron discharge device; a tunable output circuit, tuned to a harmonic of the fundamental frequency, directly connected to the output terminals of the electron dischar e device; means for subjectingthe control e ectrode of the .device to a negative potential such that only narrow positive peaks offundamental frequency input energy cause anodev current to flow; and, means for regeneratively feeding energy of the harmonic frequency from the tuned out# put circuit to the input side of said electron discharge device.

31. In combination, a pair of electron discharge devices having their cathodes connected together; a tunable input circuit tuned to a fundamental frequency directly connected to the input terminals of said devices; a tunable output circuit tuned to a harmonic of the fundamental frequency,

directly connected to the output terminals lof said electron discharge devices; and,

means for subjecting the control electrodes of the discharge devices to negative potentials such that only narrow positivel peaks of fundamental frequency input energy cause anode current flow in the output circuits of said devices.

32. In combination, a pair of electron discharge devices having their cathodes connected together; a tunable input circuit, tuned to a fundamental frequency. directly connected to the input terminals of said devices; a tunable output circuit tuned to a harmonic of the fundamental frequency, directly connected to the output terminals of said electron discharge devices; means for subjecting the c'ontrol electrodes of -said devices to negative potentials such that only narrow positive peaks of fundamental frequency input energy cause current flow in the output circuits of said devices; and, means terminals of the electron discharge device;

a tunable output circuit, tuned to a harmonie ofthe fundamental frequency, coupled to the output terminals of the electron discharge device; means for subjecting the controlelectrodc of the device to a negative potential such that only narrow positive peaks of fundamental frequency input energy cause anode current to How; and, means for regeneratively feeding energy of the harmonic frequency from the tuned output circuit to the input side -of said electron discharge device.

84. In combination, an electron discharge device; a tunable input circuit, tuned to a fundamental frequency, coupled to the input terminals of the electron discharge device; a tunable output circuit, tuned to a harmonic of the fundamental frequency, coupled to the output terminals of the electron discharge device; and, a condenser connected in neutralizing fashion between said input and output circuits.

35. In combina-tion, an electron discharge device; a tunable input circuit, tuned to a fundamental frequency, coupled to the input terminals of the electron discharge device; a tunable output circuit, tuned to a harmonic of the fundamental frequency, coupled to the output terminals of the electron discharge device; a condenser connected in neutralizing fashion between said input and output circuits; and, means for subjecting the control electrode of the device to a negative potential such that only narrow positive peaks of fundamental frequency input energy cause anode current flow in the output circuit of the device.

8G. In combination, a pair of electron discharge devices having their cathodes connected together a tunable input circuit, tuned to a fundamental frequency, coupled in phase opposition tol the input terminals of -said devices; a tunable output circuit, tuned to a harmonic of the fundamental frequency, coupled to output terminals of said electron dis- I 37. In combination, a pair of electron discharge devices having their cathodes connected together; a tunable input circuit tuned to a fundamental frequency directly connected in phase opposition te the input terminals of said devices; a tunable output circuit tuned to a harmonic of the fundamental frequency, directly connected to the output terminals of said electron discharge devices; means for subjecting the control electrodes of the discharge devices to negative potentials such that only narrow positive peaks of fundamental frequency input energy cause anode current flow in the output circuits of said devices, and means for preventin undesired capacitive feed back action cause by the interelectrode capacitance between input and output electrodes of said devices.

38. A frequency multiplier comprising an electron discharge device having within an hermetically sealed container an electron emitting cathode and anode and a control electrode, a circuit tuned to a fundamental fre-y quency coupled to said control electrode and cathode, and, an output circuit for said electron discharge device tuned to a harmonic frequency of said fundamental coupled to the anode and cathode of said device, and, means, for preventing regenerative amplification of electrical energy of fundamental frequency, associated with said electron discharge device.

CLARENCE W. 'HANSELL 

